Serogroup Y Meningococcal Disease -- Illinois, Connecticut, and Selected Areas, United States, 1989-1996

Neisseria meningitidis is a leading cause of bacterial meningitis and sepsis in the United States. N. meningitidis is classified into serogroups based on the antigenic characteristics of its capsular polysaccharide. During 1989-1991 in the United States, serogroups B and C accounted for most (91%) of invasive meningococcal disease while serogroup Y caused less than 5% (1); however, during 1992-1995, serogroup Y accounted for an increasing proportion of meningococcal disease. This report describes the epidemiology of serogroup Y meningococcal disease (SYMD) during 1991-1996 in Illinois and Connecticut, which conducted enhanced surveillance through active reviews of clinical records, and in areas participating in active laboratory-based surveillance during 1989-1995. The findings indicate a substantial increase in the proportion of meningococcal disease caused by N. meningitidis serogroup Y since 1989.

Illinois

In Illinois (1990 population: 11,430,602), 589 cases of invasive disease attributed to N. meningitidis were reported from January 1991 through March 1996, representing an annual incidence ranging from 0.9 to 1.0 per 100,000 population. Serogrouping was conducted for 371 (83%) of 447 culture-confirmed cases. The proportion of SYMD increased from 6% in 1991 to 29% in 1995; the proportion of disease attributed to serogroups B and C decreased from 85% to 59%.

From January 1991 through March 1996, the Chicago Department of Public Health received 145 reports of suspected meningococcal disease among persons residing in Chicago (1990 population: 2,783,726), and N. meningitidis was isolated from a normally sterile site in 133 (92%) case-patients. The overall annual incidence of culture-confirmed disease ranged from 0.7 to 1.3 cases per 100,000 population. Of the 105 culture-confirmed isolates for which serogroup was known, 42 (40%) were serogroup Y; 29 (28%), serogroup B; 27 (26%), serogroup C; and two (2%), serogroup W-135. Among case-patients with known serogroups, the proportion of SYMD increased from 6% in 1991 to 71% in 1995. In comparison, the proportion of serogroups B and C decreased from 94% to 25%. Of 42 patients in Chicago with culture-confirmed SYMD, 22 (52%) were female; two (5%) died. The median age of patients with SYMD was 16 years compared with 2 years for patients with disease caused by non-serogroup Y meningococci. Although patients with SYMD were more likely to present with purulent sputum (six {14%} versus one {2%}) and chest pain (eight {19%} versus one {2%}), they were not more likely to have an infiltrate on chest radiograph (seven {23%} versus 10 {20%}). Case-fatality rates were similar among patients with SYMD (two {5%} of 42), compared with case-patients with disease caused by other known serogroups (six {10%} of 63).

Connecticut

From January 1991 through June 1996, a total of 190 culture-confirmed cases of invasive N. meningitidis infection among residents of Connecticut (1990 population: 3,287,116) were reported to the Connecticut Department of Public Health. The overall annual incidence of culture-confirmed cases ranged from 0.7 to 1.4 per 100,000 population. Of the 144 isolates for which serogroup was known, 69 (48%) were serogroup C; 38 (26%), serogroup Y; 35 (24%), serogroup B; and two (1%), serogroup W-135. The proportion of SYMD increased from 1991 (6%) to 1995 (35%). Of the 33 case-patients with SYMD identified since 1994, 18 (55%) were female; two (6%) died. The median age for patients with SYMD was 29 years, compared with 13 years for patients with disease caused by non-SYMD.

Active Laboratory-Based Surveillance

During 1989-1995, active laboratory-based surveillance was conducted in three counties in the San Francisco metropolitan area, eight counties in the Atlanta metropolitan area, and four counties in Tennessee, and during 1992-1995, in Maryland, representing an aggregate population of approximately 12 million. A case was defined as N. meningitidis isolated from a normally sterile site in a resident of a surveillance area. In the three active surveillance areas for which continuous data were available, the rate of SYMD per 100,000 persons increased from 1989 (0) to 1995 (0.4). Among the case-patients for whom serogroup was known, the proportion of SYMD increased from 1989 (0) to 1995 (32.5%). During the same period, the overall rate of meningococcal disease remained stable at 1.0-1.4.

During 1992-1995, in the four active surveillance areas, SYMD patients were older than patients with non-serogroup Y (median age: 21.8 years versus 14.2 years). Pneumonia was four times more likely to be diagnosed in persons with SYMD (12%) than in persons with other serogroups (3%), even after adjusting for age.

Laboratory Investigation

Multilocus enzyme electrophoresis (MEE) (2) using 24 enzymes was used to characterize genetic relatedness of serogroup Y isolates systematically sampled from 1995 Illinois surveillance (n=40), 1995 Connecticut surveillance (n=17), 1992-1995 U.S. active laboratory-based surveillance (n=40), 1972-1975 U.S. active laboratory-based surveillance (when SYMD accounted for 18% of the isolates submitted to CDC) (n=27) (3), and 1970-1974 surveillance of U.S. military personnel (n=12). Two major enzyme type complexes could be distinguished by a difference in peptidase mobility. One group of enzyme types accounted for 54% (33 of 97) of the isolates tested during 1992-1995, one of the 1972-1975 surveillance strains, and none of the strains from U.S. military personnel. The other group accounted for 34% (33 of 97) of 1992-1995 isolates and 62% (24 of 39) of the 1972-1975 isolates.

Reported by: J Racoosin, MD, PS Diaz, MD, U Samala, MPH, B Clark, D Freedman, MD, W Paul, MD, Chicago Dept of Public Health; M Swartz, K Kelly, C Langkop, MSPH, Illinois Dept of Public Health. R Nelson, DVM, M Cartter, MD, P Mshar, JL Hadler, MD, State Epidemiologist, Connecticut Dept of Public Health. W Baughman, MSPH, M Farley, MD, E Houpt, MD, D Stephens, MD, Veterans Administration Medical Svcs and Emory Univ School of Medicine, Atlanta. L Billman, MPH, L Harrison, MD, Johns Hopkins Univ, Baltimore; D Dwyer, MD, Maryland Dept of Health and Mental Hygiene. B Barnes, L Lefkowitz, MD, Vanderbilt Medical Center, Nashville, Tennessee. G Rothrock, MPH, A Reingold, MD, Emerging Infections Program, San Francisco. W Zollinger, MD, Walter Reed Army Research Institute, Bethesda, Maryland. Childhood and Respiratory Diseases Br, Div of Bacterial and Mycotic Diseases, National Center for Infectious Diseases; Div of Applied Public Health Training (proposed), Epidemiology Program Office, CDC.

Editorial Note

Editorial Note: During the 1970s, SYMD was recognized as a common cause of endemic disease in some U.S. populations (3,4) and was associated with several outbreaks in military personnel (5-7). During 1978-1981, SYMD caused 7% of meningococcal cases reported through a nationwide surveillance system in which 27 states participated (8). Although SYMD accounted for only 2% of endemic disease in U.S. active surveillance during 1989-1991 (1), by 1995 the proportion of infections caused by SYMD had increased in Illinois and Connecticut and in the active surveillance areas. In 1995, among the 30 states reporting supplemental data on culture-confirmed cases of meningococcal disease through the National Electronic Telecommunications System for Surveillance (NETSS) (9), serogroup information was recorded for 527 (54%) of 973 cases reported, and serogroup Y accounted for 21% of cases. This pattern is consistent with the findings in this report and underscores the need to both determine and report serogroup information for all cases of meningococcal disease.

The finding in this report that patients with SYMD in Chicago, Connecticut, and the active laboratory-based surveillance areas were older than patients with disease caused by non-serogroup Y meningococci is consistent with cases reported to CDC through NETSS. One possible explanation for this and the increase in SYMD is waning population immunity against SYMD. However, the increase in SYMD also may reflect, in part, the emergence of a distinct clone that differs in peptidase motility, as characterized by MEE. Although the association between epidemic meningococcal disease and clonality has been clearly established, the possible relation between shifts in endemic disease serogroup distribution and emergence of particular clones requires further assessment.

The clinical illness associated with SYMD differs from that of the other serogroups; in particular, findings from the active laboratory-based surveillance system indicated that pneumonia was more common among patients with SYMD, consistent with studies in some military populations (5,6) in which serogroup Y was more likely than other serogroups to be associated with pneumonia and other forms of nonmeningitic disease. Meningococcal pneumonia may not be diagnosed because isolation of the organism from the sputum cannot distinguish persons who are meningococcal carriers from those with pneumonia caused by this organism, and because physicians may not consider N. meningitidis as a possible cause of pneumonia. As a result, infections that occur in the absence of meningitis or bacteremia may be underreported in current surveillance.

The current meningococcal vaccine (Connaught Laboratories, Swiftwater, Pennsylvania), which contains the purified polysaccharide capsules of serogroups A, C, W-135 and Y, has been effective in controlling serogroup C outbreaks and may be useful in controlling an SYMD outbreak. However, this vaccine has not been used to control endemic disease because its immunogenicity is low in young children and immunity is of limited duration. Conjugated vaccines for serogroup C, which are similar to those now available for preventing Haemophilus influenzae type b, are being evaluated in safety and immunogenicity trials (10). Because of the increased proportion of SYMD, manufacturers should consider developing a serogroup Y conjugate component for controlling endemic meningococcal disease.

References

1. Jackson LA, Wenger JD. Laboratory-based surveillance for meningococcal disease in selected areas, United States, 1989-1991. In: CDC surveillance summaries (June). MMWR 1993;42(no. SS-2):21-30.

2. Selander SK, Caugant DA, Ochman H, Musser JM, Gilmour MN, Whittam TS. Methods of multilocus enzyme electrophoresis for bacterial population genetics and systematics. Appl Environ Microbiol 1986;51:873-84.

3. Anonymous. Analysis of endemic meningococcal disease by serogroup and evaluation of chemoprophylaxis. J Infect Dis 1976;134:201-4.

4. Galaid EI, Cherubin CE, Marr JS, Schaefler S, Barone J, Lee W. Meningococcal disease in New York City, 1973 to 1978: recognition of groups Y and W-135 as frequent pathogens. JAMA 1980;244:2167-71.

5. Koppes GM, Ellenbogen C, Gebhart RJ. Group Y meningococcal disease in United States Air Force recruits. Amer J Med 1977;62:661-6.

6. Smilack JD. Group Y meningococcal disease: twelve cases at an army training center. Ann Intern Med 1974;81:740-5.

7. Risko JA, Hodges GR. Neisseria meningitidis serogroup Y: incidence and description of clinical illness. Amer J Med Sci 1974;267:345-52.

8. Schlech WF III, Ward JI, Band JD, Hightower A, Fraser DW, Broome CV. Bacterial meningitis in the United States, 1978 through 1981: the National Bacterial Meningitis Surveillance Study. JAMA 1985;253: 1749-54.

9. CDC. National Electronic Telecommunications System for Surveillance -- United States, 1990-1991. MMWR 1991;40:502-3.

10. Lieberman JM, Chiu SS, Wong VK, et al. Safety and immunogenicity of a serogroups A/C Neisseria meningitidis oligosaccharide-protein conjugate vaccine in young children: a randomized controlled trial. JAMA 1996;275:1499-503.

    
    

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